Standardization of 3GPP (The 3rd Generation Partnership Project, the 3rd generation partnership project) develops a brand-new evolved network, and SAE (System Architecture Evolution, system architecture evolution) of the evolved network is as shown in FIG. 1. In an SAE architecture, after a UE (User Equipment, user equipment) is accessed to an E-UTRAN (Evolved Universal Terrestrial Radio Access Network, evolved universal terrestrial radio access network) through a wireless air interface, the UE is firstly attached to an MME (Mobility Management Entity, mobility management entity). The MME acquires subscription data and authentication information of a user from an HSS (Home Subscriber Server, home subscriber server), and initiates a process for authenticating the UE. After the MME completes the authentication process, the UE or the MME initiates a process for establishing a bearer for transmitting user data. In this process, the MME notifies an S-GW (Serving Gateway, serving gateway) of establishing the bearer for the user, which is used for transmitting user data from the E-UTRAN to a P-GW (Packet Data Network Gateway, packet data network gateway), and the notification message carries an address of the P-GW and address information of an E-UTRAN network element where the user is located. The P-GW forwards downlink data from an external PDN (Packet Data Network, packet data network) to the UE through the bearer, and forwards uplink data from the UE to a corresponding PDN.
In order to be compatible with existing UTRAN (Universal Terrestrial Radio Access Network, universal terrestrial radio access network) and GERAN (Global System for Mobile communications/Enhanced Data rates for GSM Evolution Radio Access Network, GSM/EDGE radio access network), a UE may access an MME through a UTRAN or a GERAN, and an SGSN (Serving GPRS (General Packet Radio Service, General Packet Radio Service) Support Node, serving GPRS support node), and may establish a GTP (GPRS Tunnel Protocol, GPRS tunnel protocol) tunnel connection with an S-GW through a UTRAN/GERAN and an SGSN. The S-GW converts a GTP tunnel into a corresponding bearer connected to a P-GW which is used for transmitting user data. The UTRAN may also directly establish a GTP tunnel connected to an S-GW. An MME becomes a network element for only processing control plane signaling, and an S-GW and a P-GW are primarily responsible for forwarding user plane data. An S-GW and a P-GW may be combined into a network element, which may be referred to as a unified gateway (UGW).
With development of mobile internet services, abundance of enterprise network services and fusion of mobile access networks with multiple technologies, a gateway device needs to gradually develop towards more fine service control and charging based on realization of a basic data forwarding function, thus supporting more abundant service implementation and control of an operator. Meanwhile, in an evolved network, a UGW still needs to reserve a great number of external signaling interfaces. These signaling interfaces include a GTP-C (GTP control plane) bearer interface between an MME and a gateway, a PCC (Policy and Charging Control, policy and charging control) interface between a PCRF (Policy and Charging Rules Function, policy and charging rules function) and a gateway, a charging interface between a charging system and a gateway, a legitimate listening interface between legitimate listening device and a gateway, a DHCP interface between a DHCP (Dynamic Host Configuration Protocol, dynamic host configuration protocol) server and a gateway, an interface between an AAA (Authentication, Authorization and Accounting, Authentication, Authorization and Accounting) server and a gateway and the like.
In order to enable a gateway to be capable of processing a great amount of interface signaling, a large number of hardwares such as a general computing processor chip and the like are added on the basis of a dedicated hardware platform, which makes a hardware platform of a gateway device quite complex and cost too much, thus is unfavorable for spread and deployment of a mobile packet data network.
For solving the above-mentioned problem, a scenerio where a control plane and a forwarding plane of a gateway are separated appears at present, namely a gateway is divided into a unified gateway control plane UGW-C and a unified gateway forwarding plane UGW-U according to functionality, and an interface between the UGW-C and the UGW-U is defined as Sg. The UGW-C processes external signaling interaction, including interaction with an AAA server, interaction with a PCRF by using PCC signaling and the like. The UGW-C completes signaling negotiation and sends information needed for forwarding a data packet by the UGW-U (referred to as context information) to the UGW-U, and the UGW-U forwards user data packet according to the context information indicated by the UGW-C. Similar decoupling concept may be applied to an SGSN and a GGSN of a 2G/3G network or to an S-GW and a P-GW independent deployment device under the SAE architecture.
It is needed to consider that, under the scenario that the control plane and the forwarding plane of the gateway are separated, how to execute forwarding of a data packet when a gateway forwarding plane device loses context information corresponding to the data packet.